Just completed a full basement underpinning project on our 1947 Toronto semi in the Roncesvalles area. Previous ceiling height was 6’1" — not legally rentable and barely livable. Now sitting at 7’9". Sharing the full project diary.
Why we underpinned:
We wanted to convert the basement into a legal secondary suite. At 6’1", we were 4 inches below the 6’5" code minimum. The engineer confirmed full underpinning was the only option (no benching — the footings were original stone rubble, not poured concrete).
Engineer and permit:
Structural engineer: $3,400 for drawings and site visits
Toronto building permit: $2,280
Total pre-construction cost: $5,680
Contractor quotes (full underpinning + new slab):
- Quote A: $68,000
- Quote B: $57,500
- Quote C: $74,000
We went with Quote B — the contractor had done 40+ underpinnings in the Roncesvalles/Parkdale area. References were excellent.
Timeline:
- Start to new slab pour: 11 weeks
- 22 pins total (every 4 feet around perimeter)
- Each pin: dig out section, pour new footing, cure, move to next
- Settlement monitoring with reference points throughout
Key moments:
- Found an underground spring on the north wall in week 3 — required drainage adjustment ($2,800 extra)
- One pin had to be re-poured after inspector found voids (no cost to us — contractor’s scope)
Final cost: $62,100 (over quote by $4,600 due to the spring drainage)
Post-underpinning next steps:
New slab poured, now framing the secondary suite. Planning to have it rented by July at $1,950/month.
Happy to answer any questions — this was the most intense renovation we’ve done and the most worth it.